Two step preparation of aluminum alkoxides



United States Patent 3,097,226 TWO STEP PREPARATION OF ALUMINUM ALKOXIDES Donald R. Napier, Ponca City, Okla, assignor to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Filed July 25, 1961, Ser. No. 126,498

6 Claims. (Cl. 260-448) This invention relates to an improved method of-oxidizing aluminum trialkyls [to produce aluminum ftrialk'oxides, and more particularly the present invention is concerned with an economical method of effecting such an oxidation reaction.

Alcohols may be produced from the hydrolysis of aluminum trialkoxides. The aluminum trialkyls from which the alkoxides are produced may be derived from the wellknown growth reaction between a low molecular aluminum trialkyl and an alpha-olefin, such as ethylene. An important step in the over-all process is the oxidation of the higher molecular weight aluminum trialkyls into the corresponding aluminum trialkoxides. In the oxidation step, side reactions occur resulting in the formation of such by-products as aldehydes, esters and hydrocarbons. The formation of by-products increases with temperature; consequently it is preferable to conduct the process .at the lowest temperature which is consistent with a reasonable reaction rate. Unfortunately, however, temperatures below normal room temperature (i.e., about 20 C.) are attained through the use of expensive cooling equipment, which may render the process less attractive economically in certain situations. It was found that the preferred oxidation temperature is below normal room temperature, and for that reason a search was made for a method which could improve the economics of the process. This invention is concerned with such an improved method, and accordingly such method constitutes an important object thereof.

Another object is to provide a substantially more economical method of oxidizing aluminum trialkyls to produce aluminum trialkoxides.

Other objects and advantages will become apparent from the following explanation and description thereof.

and then subsequently the oxidation reaction is conducted at below normal room temperature, usually about l0 to 15 C. to obtain a higher yield of trialkoxide product.

The oxidation of aluminum trialkyl is preliminarily conducted with a view of effecting the highest yield of trialkoxide product consistent with minimum production of by-products. The first stage of oxidation is'done at a temperature above normal room temperature so that no expensive cooling equipment is required. Quite surprisingly by controlling the reaction to provide a yield of not morethan about 70 percent, usually about 45 to 65 percent, preferably about to 60'percent, the use of a temperature abovenormal room during the first stage appears to have no adverse effect in the over-all yield, when compared with an operation in whichthe entire reaction 'was conducted at a temperature below normal room; In the first stage, the aluminum-trialkyLwith orwithout'a solvent, is contacted with the oxygen containing gas in an amount of'about 300 to 1,000 stan da-rd cubic feet per pound mole'aluminum in the aluminum trialkyl, abbreviated as rs. c.f. (measured at 0" .C- and 760 Hg),

3,097,226 Patented July 9, 1963 more usually about 700 to 800 s.c.f. per pound mole of aluminum. The temperature of reaction is usually between about 25 and C., more usually about 40 to 60 C. The reaction pressure can be varied widely, but generally it is about 15 to 50 p.s.i.g. The reaction time varies from about 1 to 50 hours, more usually about 3 to 7 hours. If desired, the first stage can comprise a series of oxidative steps or a single operation in which the yield of trialkoxide is obtained.

In the second stage of oxidation, the temperature is dropped to below normal room, and the reaction is completed to provide a yield greater than about 70- percent. For this purpose, the temperature of reaction is from about 10 to 15 C., more usually about 5 to 55C. By virtue of the lower reaction temperature, the formation of by-products is minimized. The overall yield resulting from the second stage is usually about to 98 percent. The amount of oxygen containing gas employed relative to the reaction mass is about 50 to .160 sLc.f. per pound, more usually about to s.c.f. per pound. The re actionis conducted at widely varying pressures, however, usually about 15 to 5 0 p.s.i.g. The second stage can be a single operation or a series of steps making up the same.

The first and second stages of oxidation can be conducted as either batch or continuous operations. In the continuous ope-ration, the oxygen containing gas and the feed material are charged, on a time basis, in the same relative proportions as specified hereinabove. The liquid reactant is contained in the oxidation vessel as a holdup 'so that the residence time may vary from about 1 to 5 0 hours, more usually about 3 to 7 hours.

The aluminum trialkyl-employed as a starting materi has the following structural formula: r

. Bi .Al Rn R: in which R R and R may be the same or different alkyl groups containing from about 4 to 30 carbon atoms or higher.

In one method of preparation, these aluminum trialkyls are obtained through the reaction of a low molecular weight aluminum alkyl with a lower olefin, for example, ethylene, to form the so-called aluminum trialkyl growth product having the structural formula set forth above. The growth reaction is carried out, for example, by passing ethylene through aluminum triethyl, preferably in the presence of a diluent under a wide variety of reaction erably 90l20 C. and LOGO-3,500 p.s.i.g. It istobe understood that, instead of employing triethylalurninum as the starting trialkylaluminum in the above reactiom-other low molecular weight alkyl (C -C aluminum compounds, such as tn'propylaluminum, tributylaluminum, triisobutylaluminum, diethylaluminum hydride, ethylaluminum dihydride, etc., can be employed; and in lieu of ethylene, other low molecular weight aliphatic moriml-dlfins, such as propylene and the like can be substituted. 'Ge nerally, C -C olefins are preferred as the'growth hydrocarbon compound. 7

It is within the scopeof the invention to employ all or any portion of the growth product and also any of the individual aluminum trialkyl compounds'inthe methodiof this invention. Specific examples of 'suchcompounds are aluminum tributyl, aluminum tripentyl, aluminum trihexyl, aluminum trioctyl, aluminum tridodecyl, aluminum butyl dihexyl, aluminumhexyl dioctyl, etc.

The oxygen containing gas employed in :the oxidation reaction can beoxygen, a-iror any-other ga'scon'taining aluminumtriailkyl, with or-without a solvent. Thesolve'nt action products. .used, including liquid parafiinic hydrocarbons, aromatic aids in keeping the reaction mass fiuid and providing for better control of reaction conditions. The solvent is essentially nonreactive and easily removed from the re- Various classes of compounds can be EXAMPLE 1 The oxidation mixture consisted of 9 ml. of aluminum tn'hexyl and 15 ml. of n-decane. The reaction times were 12 hours at C. and five hours at 30, 45, 60 and 75 C. The air rate was 120 ml. per minute, and the pressure was 760 mm. of HgiS mm. At the end of the reaction time, 30 ml. of decane was added, and

the solution was stirred vigorously while adding 25 percent HCl and cooling to 10l5 C. The reaction mass was then stirred for an additional one-half hour at room temperature. The organic phase of the reaction was washed twice with 15 ml. portions of water and dried.

The acid phase and water extracts were combined and then extracted twice with 20 ml. portions of decane. The decane extracts were dried. The products were then analyzed, the results being given in Table I.

The results in Table I illustrate the effect in temperature on alcohol yield. It is noted that as the reaction temperature is increased, the percent yield of alcohol steadily decreases.

EXAMPLE 2 In another series of experiments, the reaction conditions described above were used, except that the temperature was maintained at 55 ':0.5 C. during the first 40-60 percent conversion and then reduced rapidly in 45-55 seconds to 0 C. where it was held to the end of the reaction.

I'he results of this experiment are given below in Table H:

Table 11 Reaction temp., Alcohol, Run No. 0. percent yield The results in Tables I and II demonstrate the unusual efieot of conducting the reaction in two stages. It should be noted that Run 1 in Table I is a single stage run at 0 C. and gave a yield of 94 percent; whereas Runs 1, 2 and 3 of Table II gave excellent yields in two stages. The two-stage operation compares very well with the run at 0 C.

EXAMPLE 3 Aluminum trialkyl growth product was prepared by reacting aluminum triethyl with ethylene at a temperature of 120 C. and a pressure of 1,500 p.s.i.g. for about 2.5 hours. The product which had an "m value of 3.8 was oxidized in a series of runs with air or oxygen for time periods ranging from 5 to 12 hours in the presence of a solvent, the product being hydrolyzed and extracted to obtain the organic portion of the product. The percent yields of alcohol in each run were then ascertained, the results being presented in Table III:

Table III Reaction Alcohol, Run N0. temp., percent 0. yield 1 The average number of ethylene units added to each alkyl aluminum bond of the aluminum triethyl.

The data in 'Iable III again illustrate that increasing reaction temperatures cause a reduction in alcohol yield as previously noted in Example 1.

Having thus described the invention by providing specific examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by reason thereof and that many variations and modifications are within the scope of the invention.

I claim:

1. A process which comprises (1) first reacting aluminum alkyl growth product with an elemental oxygen containing gas at a temperature above normal room temperature not exceeding about 70 C. to effect a substantial conversion to the alkoxide but not more than about 70 percent and (2) thereafter reducing the temperature to below the reaction temperature of the first step, reacting the unreacted trialkyl growth product with elemental oxygen containing gas at said temperature below normal room temperature not below about 10 C. to efiect significantly more conversion to aluminum alkoxide than would result from continuing the reaction at the temperature of the first step for the same length of time.

2. A process which comprises 1) first reacting aluminum trialkyls having alkyl groups containing about 4 to 30 carbon atoms per group with an elemental oxygen containing gas at a temperature above normal room temperature not exceeding about 70 C. to eifect a substan tial conversion to the alkoxide but not more than about 70 percent and (2) thereafter reducing the temperature to below the reaction temperature of the first step, reacting the unreacted aluminum trialkyl with elemental oxygen containing gas at said temperature below normal room temperature but not below about 10 C. to efiect significantly more conversion to aluminum alkoxide than would result from continuing the reaction at the temperature of the first step for the same length of time.

3. The process of claim 2 wherein the first-mentioned temperature is about 25 to 70 C. and the first mentioned conversion is about 45 to 65 percent.

4. The process of claim 3 wherein the second-named temperature is about -10 to 15 C. and the total conversion is about to 98 percent.

5. A process which comprises. reacting aluminum trialkyl having about 4 to 30 carbon atoms per group with an elemental oxygen containing gas at a temperature of about 40 to 60 C. to effect a conversion to the alkoxide of about 45 to 65 percent and then contacting the resultant reaction product with elemental oxygen containing gas at a temperature of about -5 to 5 C. to eflect a total conversion to the alkoxide of about 80 to 98 percent.

6. The process of claim 5 wherein the aluminum trialkyl has about 6 to 12 carbon atoms per group.

2,892,858 Ziegler June 30, 1959 

1. A PROCESS WHICH COMPRISES (1) FIRST REACTING ALUMINUM ALKYL GROWTH PRODUCT WITH AN ELEMENTAL OXYGEN CONTAINING GAS AT A TEMPERATURE ABOUT NORMAL ROOM TEMPERATURE NOT EXCEEDING ABOUT 70* C. TO EFFECT A SUBSTANTIAL CONVERSION TO THE ALKOXIDE BUT NOT MORE THAN ABOUT 70 PERCENT AND (2) THEREAFTER REDUCING THE TEMPERATURE TO BELOW THE REACTION TEMPERATURE OF THE FIRST STEP, REACTING THE UNREACTED TRIALKYL GROUP PRODUCT WITH ELEMENTAL OXYGEN CONTAINING GAS AT SAID TEMPERATURE BELOW NORMAL ROOM TEMPERATURE NOT BELOW ABOUT -10* C. TO EFFECT SIGNIFICANTLY MORE CONVERSION TO ALUMINUM ALKOXIDE THAN WOULD RESULT FROM CONTINUING THE REACTION AT THE TEMPERATURE OF THE FIRST STEP OF THE SAME LENGTH OF TIME. 